JP2019020625A - Exhauster and image formation apparatus - Google Patents

Abstract

To provide an exhauster which can suppress reduction in the heat discharge efficiency by stably rotating two fans having the different air capacities and prevent the generation of the howling noise.SOLUTION: In an exhauster which discharges the air to the outside of the device by taking the heated air in the upper space of a fixation unit into a duct in an image formation apparatus, a fan 61 and a fan 62 having the smaller air capacity than the fan 61 are arranged in the vicinity of a discharge port in the duct, only the fan 61 having the larger air capacity is operated when the temperature of a fixation roller is lower than Tb during warm-up, the fan 62 having the smaller air capacity is started up (time point t6) after the rotation of the fan 61 is temporarily stopped (time point t5) when the temperature is equal to or greater than Tb, the fan 61 is started up (time point t7) when the fan 62 reaches the stable rotation, and then, both of fans 61, 62 are operated.SELECTED DRAWING: Figure 6

Description

  The present invention relates to an exhaust apparatus and an image forming apparatus for discharging air in an image forming apparatus such as a copying machine, a printer, and a multifunction peripheral to the outside of the image forming apparatus.

In an electrophotographic image forming apparatus, an unfixed image such as a toner image formed on a recording sheet is thermally fixed using a fixing member heated by a heater. In this configuration, the temperature in the image forming apparatus is likely to increase due to the heat of the heater, and if the temperature of the developing unit in the apparatus, for example, is excessively high, there is a risk of developing performance deterioration such as solidification of toner in the developing unit. .
In order to prevent the temperature inside the apparatus from rising excessively, an exhaust device that takes in air that has risen in the apparatus into the duct by a fan and discharges the taken air out of the image forming apparatus by the duct to cool the inside of the apparatus. It is installed.

JP 2007-322470 A JP 2011-33337 A

As a configuration of the exhaust device, two fans having different air volumes (amount of air moved per unit time: m ³ / h) are arranged in one air passage, for example, in the vicinity of the duct outlet, and the temperature in the device is If only one fan is operated when the power is low, such as immediately after the power is turned on, and both fans are operated when the power is very high, such as during printing, image formation is performed by combining two relatively inexpensive fans. The exhaust heat according to the temperature change in the apparatus can be efficiently performed.

When operating these two fans, if the start timing of each fan is shifted, a large start-up current flows to both fans at the same time, and the current load on the power supply temporarily increases extremely. Can be avoided.
However, if the start order of the startup is the order of the fan with the larger air volume (large fan) and the fan with the smaller air volume (small fan), the following problems occur. That is, when the small fan is activated, the large fan is already rotating, and the air flow of the large fan tends to affect the rotation of the small fan that is about to start up.

  For example, in a configuration in which a large fan and a small fan are arranged in parallel in a direction perpendicular to the length direction of the duct, the large fan inlet side and the small fan inlet side in the direction of air flow in the duct And share the same space. Therefore, in the duct, when the air pressure on the inlet side of the large fan in operation is lower than the space on the outlet side, the inlet side of the small fan that has not been started yet has been stopped. The air pressure in the space also decreases.

When the air pressure is reduced and a reverse flow occurs in the small fan that is stopped driving, the air flows from the blower outlet to the intake port through the internal rotary blades. Produces a force to rotate in the opposite direction. This force becomes a load when starting the motor of the small fan and weakens the rotational driving force.
When the motor is started, inertia of each member such as a rotating blade of the fan, a rotating shaft and a gear that transmits power to the fan acts on the motor, and a lot of energy required for rotation is required.

  When the small fan starts after the large fan starts, the above load is added separately from the inertia when the small fan starts, and the energy required for rotation is deprived by that load, The rising rotation at the time of starting the small fan tends to be unstable. Due to the unstable rotation of the small fan at the time of startup, the time until the small fan reaches the rated rotation speed becomes longer, the air volume becomes insufficient and the exhaust heat efficiency decreases, or the wind noise of the rotating blades of the small fan is heard. It can be annoying to the user and make the user feel uncomfortable.

Such a problem is not limited to the configuration in which two fans are arranged in the vicinity of the discharge port of the duct. Since the space on the intake port side is common in the duct, when the large fan operates, This similarly occurs in the positional relationship where the air pressure on the fan inlet side is lower than that on the air outlet side.
Further, the configuration is not limited to the configuration in which the space around the fixing member is cooled. For example, when ozone generated by the discharge of the charging unit is discharged, the same problem occurs even in a configuration in which the airflow of the airflow flowing in the duct is varied. Furthermore, the present invention is not limited to the electrophotographic system, and for example, an ink jet image forming apparatus may similarly occur in a configuration in which air inside the apparatus is discharged to the outside.

  SUMMARY An advantage of some aspects of the invention is that it provides an exhaust apparatus and an image forming apparatus that can stably rotate two fans having different air volumes.

  In order to achieve the above object, an exhaust apparatus according to the present invention is an exhaust apparatus that takes in air in an image forming apparatus into a duct and exhausts the taken-in air out of the image forming apparatus from the duct. 1 fan, a second fan having a smaller air volume, and control means for controlling the first and second fans, wherein the first and second fans are air passages in the duct. When the first fan operates while the second fan is stopped driving, the air intake side of the second fan is disposed in a positional relationship such that the air pressure is lower than the air outlet side. When the control means receives the operation instructions for both of the first and second fans, and when both fans are stopped, the control means starts the first fan after starting the second fan. 1 control is performed, and the first fan When the second fan is in operation and the driving of the second fan is stopped, the second fan is started after the rotation of the first fan is stopped or due to a decrease in the atmospheric pressure accompanying the operation of the first fan. The rotation speed is reduced to a predetermined speed so as not to affect the operation, the second fan is started, and then the first fan is started or the second control for returning the rotation speed is executed. It is characterized by doing.

  Further, the control unit acquires the temperature in the apparatus from the image forming apparatus, and operates the first fan and drives the second fan when the acquired temperature in the apparatus is lower than a predetermined temperature. The third control to be stopped may be executed, and when the acquired temperature rises and reaches the predetermined temperature, this may be accepted as the operation instruction and switched from the third control to the execution of the second control.

Here, when the control means determines that the acquired temperature is equal to or higher than the predetermined temperature while both the first and second fans are stopped driving, the control means accepts this as the operation instruction, and The first control may be executed.
The image forming apparatus includes a fixing unit that heat-fixes an unfixed image formed on the recording sheet by a fixing member heated by a heater, and the fixing unit is accompanied by generation of ultrafine particles during driving. The air inlet of the duct is located in the vicinity of the fixing unit, and air around the fixing unit is taken into the duct as air in the image forming apparatus, and the exhaust device is installed in the duct. It is good also as providing the collection | recovery part which collect | recovers the ultrafine particles contained in the air taken in.

  Here, the image forming apparatus further includes a detection unit that detects the temperature of the fixing member, and controls the heater based on the detection temperature of the detection unit to raise the fixing member to a fixing temperature necessary for thermal fixing. A heating controller for heating, the temperature of the fixing member and the amount of ultrafine particles generated are increased to a maximum value as the amount of the ultrafine particles is increased as the temperature of the fixing member is changed from a low temperature to a high temperature, After that, the control means acquires the detection temperature of the detection unit as the temperature in the device, and the predetermined temperature is a value after the amount of generated ultrafine particles starts to decrease from the maximum value. The temperature may be determined in advance as a temperature at which the first and second fans are operated to cool the image forming apparatus.

  Here, the recovery unit is a filter that allows the air in the duct to pass through, and a different type of ultrafine particle recovery capability is attached to the duct so that it can be replaced by an operator. According to the type of filter that is currently installed, the fan to be operated when the detected temperature is lower than the predetermined temperature is determined among the first and second fans, and is determined as the first fan. If the detected temperature is lower than the predetermined temperature, the third control is executed. When the detected temperature reaches the predetermined temperature, the control is switched to the second control. When the second fan is determined, the third control is performed. And prohibiting the execution of the second control, and executing the fourth control to start the second fan in a state where the driving of the first fan is stopped when the detected temperature is lower than the predetermined temperature, Said place Upon reaching the temperature, may be switched to the fifth control for activating said first fan while continuing the operation of the second fan.

  Here, the control means stores fan information that associates a fan to be operated when the detected temperature is lower than the predetermined temperature among the first and second fans for each different type of the filter. The filter information indicating the type of filter that is currently installed is acquired, the fan corresponding to the filter type indicated by the acquired filter information is determined from the fan information, and the determination is made. The fan may be determined as a fan that is operated when the detected temperature is lower than the predetermined temperature.

The control means may start the first fan after the second fan reaches a predetermined rotational speed after the start, or restore the rotational speed to the original.
An image forming apparatus according to the present invention is characterized in that the above-described exhaust device is mounted.

  With the above configuration, it is possible to stably rotate two fans having different air volumes, and it is possible to prevent a reduction in exhaust heat efficiency and generation of a roaring sound.

1 is a schematic cross-sectional view illustrating an overall configuration of a printer according to a first embodiment. It is a perspective view which shows the structure of a fan exhaust part. It is a perspective view which decomposes | disassembles and shows a fan exhaust part. It is arrow sectional drawing in the DD line shown in FIG. It is a block diagram which shows the structure of a whole control part. (A) is a figure which shows the relationship between the temperature of a fixing roller (broken line graph) and the amount of UFP generation (solid line graph) during warm-up of the fixing unit, and (b) is a large fan during warm-up. It is a figure which shows the operation | movement timing of a small fan. It is a figure which shows the flowchart of fan operation control. (A) is a figure which illustrates the transition of the temperature of the fixing roller when the power is turned off and on after the end of the job, and (b) is a diagram showing the operation timing of the large fan and the small fan. In Embodiment 2, it is a figure which shows the structure of the fan information which matched the kind of filter and the fan which should be used in a low temperature range. It is a figure which shows the operation timing of the big fan and small fan which concern on Embodiment 2. FIG. It is a flowchart which shows the content of the process which selects and performs 1st fan operation control and 2nd fan operation control. It is a flowchart which shows the content of the subroutine of a 2nd fan operation | movement control. It is a figure which shows the operation timing which concerns on the modification of a large fan and a small fan.

Hereinafter, an exhaust apparatus and an image forming apparatus according to an embodiment of the present invention will be described with reference to the drawings, taking a tandem type color printer (hereinafter simply referred to as “printer”) as an example.
<Embodiment 1>
(1) Overall Configuration of Printer FIG. 1 is a schematic cross-sectional view showing the overall configuration of the printer 1.

As shown in FIG. 1, the printer 1 is an electrophotographic image forming apparatus, and includes an image forming unit 10, a paper feeding unit 20, a fixing unit 30, an overall control unit 40, an operation panel 50, and a fan exhaust. The unit 60 is provided.
The image forming unit 10 includes image forming units 11Y, 11M, 11C, and 11K corresponding to respective colors of Y (yellow), M (magenta), C (cyan), and K (black), and an intermediate transfer belt 13.

The image forming unit 11K includes a photosensitive drum 12, and a charging unit 16, an exposure unit 17, a developing unit 18, and a cleaner 19 arranged along the circumferential direction of the photosensitive drum 12.
The exposure unit 17 includes a light emitting element such as a laser diode, a lens, and the like. The exposure unit 17 modulates laser light according to a drive signal from the overall control unit 40 and performs exposure scanning on the photosensitive drum 12.
The photosensitive drum 12 is rotationally driven by a drive source (not shown), and after the toner remaining on the surface is removed by the cleaner 19 before receiving the exposure, the photosensitive drum 12 is uniformly charged by the charging unit 16 as described above. When exposed to the laser beam in a uniformly charged state, an electrostatic latent image is formed on the surface of the photosensitive drum 12.

The electrostatic latent image formed on the photosensitive drum 12 is developed with a developer containing toner by the developing unit 18, and thereby a K-color toner image is formed on the surface of the photosensitive drum 12. The K-color toner image is primarily transferred from the photosensitive drum 12 onto the intermediate transfer belt 13 by the primary transfer roller 14 disposed on the opposite side of the photosensitive drum 12 via the intermediate transfer belt 13.
The image forming units 11Y, 11M, and 11C have the same configuration as the image forming unit 11K, and a toner image of a corresponding color (Y, M, or C color) is formed on the photosensitive drum 12 for each image forming unit. Then, the image is primarily transferred onto the intermediate transfer belt 13 by the primary transfer roller 14.

The operation in each of the image forming units 11Y to 11K is executed at different timings so that the toner images are primarily transferred while being superimposed on the same position on the intermediate transfer belt 13. Thereby, Y to K color toner images are formed on the intermediate transfer belt 13.
The paper feed unit 20 includes a paper feed cassette 21 that stores the recording sheet S, a feeding roller 22, a transport roller 23, and a timing roller 24.

The feeding roller 22 contacts the uppermost recording sheet S of the paper feed cassette 21 and feeds it to the downstream conveyance path. The transport roller 23 transports the recording sheet S fed by the feed roller 22 toward the timing roller 24. The timing roller 24 sends the recording sheet S to the downstream side at a timing instructed by the overall control unit 40.
The color toner image that has been multiple-transferred onto the intermediate transfer belt 13 in the image forming unit 10 moves to the secondary transfer position 15 a by the rotation of the intermediate transfer belt 13.

  The recording sheet S is fed from the timing roller 24 of the paper feeding unit 20 in accordance with the movement timing of the toner image on the intermediate transfer belt 13, and the contact position between the intermediate transfer belt 13 and the secondary transfer roller 15. When the recording sheet S passes through the secondary transfer position 15a, the color toner image on the intermediate transfer belt 13 is secondarily transferred onto the recording sheet S by the secondary transfer roller 15. The recording sheet S that has passed the secondary transfer position 15 a is sent to the fixing unit 30.

The fixing unit 30 includes a fixing roller 31, a pressure roller 32, a heater 33, and a temperature detection sensor 34.
The fixing roller 31 (fixing member) is formed by laminating a silicon rubber elastic layer and a release layer in this order on the outer peripheral surface of a hollow cylindrical metal cored bar. The pressure roller 32 is formed by laminating an elastic layer or the like on the outer peripheral surface of a metal shaft with a central shaft, and presses the fixing roller 31 with an urging force such as a spring (not shown) to form a fixing nip 39.

The pressure roller 32 is rotationally driven in a direction indicated by an arrow A by a rotational driving force of a drive motor (not shown), and the fixing roller 31 rotates in a direction indicated by an arrow B following the rotation of the pressure roller 32.
The heater 33 is a long halogen heater along the axial direction of the fixing roller 31. The heater 33 is inserted into a hollow portion inside the cylinder of the fixing roller 31, generates heat by supplying power, and heats the fixing roller 31. . As a result, the temperature of the fixing roller 31 rises.

  The temperature detection sensor 34 detects the surface temperature of the fixing roller 31. Based on this detected temperature, after the surface temperature of the fixing roller 31 has been raised to a fixing temperature (for example, 170 ° C.) necessary for heat fixing, power supply (lighting) to the heater 33 is maintained so that the fixing temperature is maintained. Blocking (light-off) switching control is performed. This control is executed by the heater control unit 86 (FIG. 5) of the overall control unit 40.

When the recording sheet S conveyed by the secondary transfer roller 15 passes through the fixing nip 39 with the surface temperature of the fixing roller 31 maintained at the fixing temperature, a color toner image (undecided) on the recording sheet S. Image) is fixed by heating and pressing. Instead of the configuration using the fixing roller 31 as the fixing member, for example, a fixing belt can be used.
The recording sheet S that has passed through the fixing unit 30 is transported along the transport path to the discharge roller 25, and then is discharged from the discharge port 25 a to the outside by the discharge roller 25 and is stored in the discharge tray 26.

The operation panel 50 is disposed at a position where the user can easily operate when standing in front of the printer 1, here, at a position on the front side of the upper surface of the apparatus main body. Key for accepting setting information and registration input. Information received on the operation panel 50 is sent to the overall control unit 40.
In order to prevent the temperature inside the apparatus from rising due to the heat generated by the heater 33 of the fixing unit 30, the fan exhaust unit 60 takes in the air in the apparatus, here, around the fixing unit 30 into the duct by the fan, To cool the inside of the apparatus.

  The specific configuration of the fan exhaust unit 60 will be described in the next section. Ultra fine particles (ultra fine particles: hereinafter referred to as “UFP”) emitted from a silicon rubber elastic layer provided on the fixing roller 31 of the fixing unit 30 are described. A filter for collecting is provided in the fan exhaust part 60. The silicon rubber elastic layer may be provided only on the pressure roller 32 or may be provided on both rollers depending on the apparatus configuration.

This UFP is considered to be produced as ultrafine particles having a particle diameter of 100 nm or less by agglomeration of low-molecular siloxane in the silicon rubber when the silicon rubber reaches a high temperature, which is volatilized in the exhaust process. Further, it is considered that when the toner is heated and dissolved in the fixing unit 30, a part of the toner component is volatilized and condensed to generate UFP.
The amount of UFP released from the fixing unit 30 is extremely small and does not immediately have an adverse effect on the human body or the environment. However, recently, hesitates that people's awareness of environmental protection has increased. Even if it is a very small amount, it is desired not to release as much as possible.

(2) Configuration of Fan Exhaust Unit FIG. 2 is a perspective view showing the configuration of the fan exhaust unit 60, with a part cut away. In the figure, the X-axis direction corresponds to the left-right direction when the printer 1 is viewed from the front side, the Y-axis direction corresponds to the height direction, and the Z-axis direction corresponds to the depth direction. The direction indicated by arrow Z is the direction from the front side of the apparatus toward the back side.

As shown in the figure, the fan exhaust unit 60 includes a fan 61, a fan 62 having a smaller air volume than the fan 61, a duct 63, and a filter 64, and is disposed on the rear side of the apparatus with respect to the fixing unit 30.
The air inlet 63a of the duct 63 opens in a direction toward the fixing unit 30 and is located at a position where the air in the upper space 36 of the fixing unit 30 can be taken in, and the outlet 63b of the duct 63 extends downward. It opens toward the outside and communicates with the space outside the device.

The duct 63 is interposed between the first duct portion 71 having the intake port 63a, the third duct portion 73 having the discharge port 63b, and the first duct portion 71 and the third duct portion 73 to connect them. 2 duct portions 72.
The filter 64 is a collection filter for UFP, and is disposed in the first duct portion 71 as a collection unit for collecting UFP.

Each of the fans 61 and 62 is a blower fan, and the fan 62 has a smaller diameter runner (forward blades: not shown) than the fan 61 and has a lower rotation speed. The airflow is also reduced. Hereinafter, the fan 61 (first fan) is referred to as a large fan 61, and the fan 62 (second fan) is referred to as a small fan 62.
The large fan 61 and the small fan 62 are arranged close to each other in the third duct portion 73, and the rotation of the motor 61 a of the large fan 61 and the motor 62 a of the small fan 62 is individually controlled by the overall control unit 40.

Here, DC motors are used as the motors 61a and 62a, and the motors 61a and 62a are rotationally driven by power supply from the overall control unit 40 and stopped by power supply interruption. The large fan 61 and the small fan 62 have a positional relationship in which the air outlet 62z of the small fan 62 is closer to the outlet 63b than the air outlet 61z of the large fan 61.
The rotational drive of the large fan 61 and the small fan 62 causes an air flow in the direction from the intake port 63a to the exhaust port 63b in the duct 63. As a result, air around the fixing unit 30 is taken into (inhaled from) the air inlet 63a of the duct 63 into the duct 63, and passes through the filter 64 while the taken-in air flows through the first duct unit 71. In addition, UPF contained in the air is collected by the filter 64. Then, the air after the UPF is removed by the filter 64 flows in order from the first duct portion 71 to the second duct portion 72 and the third duct portion 73 and is discharged from the discharge port 63b to the outside of the apparatus. The A passage through which air flows in the duct 63 becomes an air passage 69.

  When the temperature of the space around the fixing unit 30 rises, both the large fan 61 and the small fan 62 are driven to rotate, and the warm air in the space around the fixing unit 30 is discharged outside the device. Aircraft) is cooled. It is also effective to reduce the amount of ultrafine particles released to the outside by providing a UFP ionization device for charging UFP in the first duct portion 71 and providing an electrostatic filter instead of a collection filter. .

FIG. 3 is an exploded perspective view showing each of the first duct portion 71, the second duct portion 72, the third duct portion 73, the large fan 61, the small fan 62, and the filter 64.
As shown in the figure, each of the first duct portion 71, the second duct portion 72, and the third duct portion 73 is a box having a plurality of through holes (through holes).
In the first duct portion 71, a through hole provided in the side wall on one end side in the Z-axis direction is an intake port 63 a, and the through hole 71 a provided in the side wall on the other end side is the side wall of the second duct portion 72. It communicates with a through hole 72a provided in 72d. The filter 64 is disposed in the first duct portion 71 at a position close to the through hole 71a.

  A large fan 61 and a small fan 62 are attached to a region on the left side of the through hole 72a in the side wall 72d of the second duct portion 72. Specifically, the large fan 61 is fixed to the side wall 72d so that the through hole 72b provided in the side wall 72d communicates with the intake port 61p of the large fan 61, and the through hole 72c provided in the side wall 72d is provided in the small fan 62. The small fan 62 is fixed to the side wall 72d so as to communicate with the intake port 62p.

The third duct portion 73 is open on the side facing the side wall 72d, and covers the large fan 61 and the small fan 62 fixed to the side wall 72d and the peripheral area thereof, and the open end of the third duct portion 73. 73a is attached to the side wall 72d.
Needless to say, the connecting portion between the first duct portion 71 and the second duct portion 72 and the connecting portion between the second duct portion 72 and the third duct portion 73 are sealed.

FIG. 4 is a cross-sectional view taken along line DD shown in FIG. 2 and shows the inside of the third duct portion 73 in plan view.
As shown in FIG. 4, the air outlet 61z of the large fan 61 is located directly above the outlet 63b, and the large fan 61 blows air from the air outlet 61z toward the outlet 63b directly below.
The air outlet 62z of the small fan 62 is positioned between the air outlet 61z and the outlet 63b of the large fan 61 in the height direction, and obstructs the flow of air blown from the air outlet 61z of the large fan 61. In order to avoid this, it is located in a position slightly shifted to the left side from the air outlet 61z of the large fan 61 in the left-right direction. The small fan 62 blows air from the air outlet 62z toward the outlet 63b obliquely below. Since the small fan 62 is closer to the discharge port 63b than the large fan 61, the air flow blown from the small fan 62 is likely to reach the discharge port 63b.

The large fan 61 and the small fan 62 having different airflows are arranged close to each other as described above, and the duct 63 itself disposed in a device that is required to be downsized is often used in a downsized manner. This is because there is often no room for one fan.
When the arrangement shown in FIGS. 2 to 4 is taken, if the start of the small fan 62 is started during the rotational drive of the large fan 61 as described above, the small fan 62 is separated from the large fan 61 in the duct 63. It is easily affected by the air flow that is blown out.

Specifically, when the large fan 61 is rotationally driven in a state where power is not supplied to the small fan 62 to stop driving, the air pressure in the third duct portion 73 (the air pressure in the space on the outlet side) is increased. On the other hand, the atmospheric pressure in the second duct portion 72 (the atmospheric pressure in the space on the intake port side) decreases (generation of differential pressure).
The intake port 61p of the large fan 61 communicates with the space in the second duct portion 72 through the through hole 72b, and the air outlet 61z of the large fan 61 communicates with the space in the third duct portion 73. ing. Similarly, the air inlet 62p of the small fan 62 communicates with the space in the second duct portion 72 through the through hole 72c, and the air outlet 62z of the small fan 62 is in the space in the third duct portion 73. Communicating with

That is, the space on the intake port 61p side of the large fan 61 and the space on the intake port 62p side of the small fan 62 are common (the intake port 61p side of the large fan 61 and the intake port 62p side of the small fan 62 are the second duct portion. 72), the space of the air outlet 61z of the large fan 61 and the space of the small fan 62 on the side of the air outlet 62z are common.
For this reason, when the above differential pressure is generated, air flows in the direction toward the intake port 62p from the air outlet 62z to the intake port 62p (the direction opposite to that during driving) in the small fan 62 whose driving is stopped ( By this reverse flow, a force (reverse force) is applied to the motor 62a through the runner of the small fan 62 to rotate in the direction opposite to the rotation at the time of driving (forward rotation).

When a reverse force is applied to the runner of the small fan 62, when the small fan 62 is activated by the start of power supply, the original forward rotation force is caused by the driving force of the motor 62a of the small fan 62. However, the reverse force that has been acting before the start-up acts as a load and weakens the force of the forward rotation.
In particular, when the motor 62a is started, inertia of each member such as a rotating shaft and a gear that transmits a driving force to the runner acts on the runner, so that much energy is required for rotation. However, if the above load is added to the motor 62a separately from the inertia at the time of starting, the energy required for the rotation is deprived by the amount of the load, and the rising rotation from the start of the small fan 62 is reversed. It is more likely to become unstable than when it is not affected by the direction force. Due to the instability of the rotation, it takes a long time to reach the rated rotation speed from the start-up, or the wind noise of the runner becomes an irritating sound that is annoying for the user.

  If it takes a long time to reach the rated rotational speed from the start, the air volume becomes insufficient, and the exhaust heat efficiency may decrease. Also, if the rotation at the time of start-up becomes unstable, the swirling flow generated by the runner will not be stable, the rectification by the scroll to rectify the swirling flow will not be stable, and the wind noise from the runner or scroll will become a roaring sound. , It may make the user feel uncomfortable.

The occurrence of such a problem is caused by receiving the influence of the air flow blown from the large fan 61 when the small fan 62 is activated (such as the action of the reverse force described above).
Therefore, in the present embodiment, the rotation of the two fans is controlled so as not to be affected by the air flow caused by the large fan 61 when the small fan 62 is activated, so that the rotation at the time of startup when the small fan 62 is activated is controlled. By stabilizing, it takes a long time to reach the rated rotation speed to prevent the reduction of exhaust heat efficiency due to the lack of air volume, and to prevent the wind noise from becoming a roaring sound. Yes.

  This rotation control is executed by the fan control unit 87 (FIG. 5) of the overall control unit 40, and includes the following first control and second control. In brief, in the first control, when both of the two fans are stopped, the small fan 62 is first activated, and after the small fan 62 reaches a stable rotational speed, the large fan 61 is activated. In the second control, when the large fan 61 is operating and the small fan 62 is not driven, the large fan 61 is temporarily stopped to rotate, and then the small fan 62 is activated so that the small fan 62 is brought to a stable rotational speed. After reaching this time, the large fan 61 starts to be activated. In this sense, the fan exhaust unit 60 and the fan control unit 87 constitute an exhaust device that takes air in the image forming apparatus into the duct 63 and exhausts the taken air out of the image forming apparatus from the duct 63.

(3) Configuration of Overall Control Unit FIG. 5 is a block diagram showing the configuration of the overall control unit 40.
The overall control unit 40 includes a communication interface (I / F) unit 81, a CPU 82, a ROM 83, a RAM 84, an image data storage unit 85, a heater control unit 86, and a fan control unit 87.

The communication I / F unit 81 is an interface for connecting to a network such as a LAN, and includes, for example, a LAN card, a LAN board, or the like.
The image data storage unit 85 stores image data of a print job received from the network via the communication I / F unit 81.
The CPU 82 controls the image forming unit 10, the paper feeding unit 20, the fixing unit 30, the operation panel 50 and the like to smoothly execute a print job based on the image data stored in the image data storage unit 85. The ROM 83 stores a program necessary for processing executed by the CPU 82, and the RAM 84 provides a work area for the CPU 82.

The heater control unit 86 controls lighting (power supply) and turning off (power supply interruption) of the heater 33 based on the temperature detected by the temperature detection sensor 34.
The fan control unit 87 performs fan operation control for controlling the operations of the large fan 61 and the small fan 62, and includes a rotation / stop instruction unit 91 and a stable rotation determination unit 92. In addition, although the same figure shows the structural example also provided with the filter information storage part 93 and the fan information storage part 94, these storage parts are not used in Embodiment 1, but are used in Embodiment 2. Therefore, explanation is omitted here.

The rotation / stop instruction unit 91 instructs the large fan 61 and the small fan 62 to individually rotate and stop driving. The rotation driving instruction is performed by supplying the rated voltage (DC voltage) of the fan as driving power, and the driving stop instruction is performed by cutting off the driving power supply.
The stable rotation determination unit 92 determines that each of the large fan 61 and the small fan 62 has reached stable rotation after starting up after starting. This determination is mainly used to determine the start start timing when starting the large fan 61 after starting the small fan 62.

The fact that stable rotation has been reached is determined for each fan as follows.
First, the stable rotation determination unit 92 acquires a pulse signal whose cycle changes according to the rotation speed output from an encoder (not shown) provided in the fan. And the present rotational speed of a fan is detected from the period of the acquired pulse signal.
If the detected current rotation speed is within a range from 0 to a predetermined constant speed, it is determined that the stable rotation has not been reached, and that the stable rotation has been reached when the rotation speed exceeds the predetermined speed. This constant speed is the rated rotational speed of the fan. If a certain degree of error or variation occurs in the detected speed, the constant speed is set to a predetermined speed lower than the rated rotational speed, such as 90% of the rated rotational speed. Also good.

(4) Content of Fan Operation Control FIG. 6A shows the relationship between the temperature T (broken line graph) of the fixing roller 31 and the UFP generation amount U (solid line graph) during the warm-up of the fixing unit 30. The horizontal axis indicates time, and the vertical axis indicates the temperature T of the fixing roller 31 and the amount of UFP generated.
Here, the warm-up operation of the fixing unit 30 is triggered by turning on the power of the printer 1 or canceling power saving (time t1), and the heater 33 is turned on, and the fixing is performed until the temperature T of the fixing roller 31 reaches the fixing temperature Ta. This is an operation for raising the temperature of the roller 31. When the temperature T of the fixing roller 31 reaches the fixing temperature Ta (time t4), the warm-up is completed, and thereafter, the heater 33 is switched on and off alternately to maintain the temperature T of the fixing roller 31 at the fixing temperature Ta. Shift to maintenance control. This warm-up and maintenance control is executed by the heater control unit 86 based on the temperature detected by the temperature detection sensor 34.

As shown by the broken line graph in FIG. 6A, the temperature T of the fixing roller 31 gradually increases as time elapses after the time point t1 when warm-up is started.
On the other hand, as shown by the solid line graph, the UFP generation amount is small at the time t1 when the temperature T of the fixing roller 31 is considerably low, such as about room temperature, and increases rapidly from the time t1 as the temperature T of the fixing roller 31 increases. The maximum value Ua is reached. When the amount of UFP reaches the maximum value Ua, the maximum value Ua remains as time passes, and starts to decrease after the time t2 when the temperature T of the fixing roller 31 rises to Tc. The rate of decrease gradually decreases from the time point t3 when the temperature T of the fixing roller 31 increases and the temperature T of the fixing roller 31 increases to Tb, and then gradually decreases to Ub. That is, when the temperature T of the fixing roller 31 starts to rise from a low temperature of about room temperature, the amount of UFP generated becomes considerably large, and the temperature T of the fixing roller 31 rises to a high temperature such as the fixing temperature Ta and then stabilizes at a constant temperature. , UFP generation amount is considerably reduced.

  From the graph shown in FIG. 6A, the UFP generation amount and the temperature T of the fixing roller 31 indicate that the UFP generation amount increases and reaches the maximum value as the temperature T of the fixing roller 31 moves from low to high. It can be seen that there is a decreasing relationship. In the low temperature range where the temperature of the fixing roller 31 is equal to or lower than Tb (for example, 120 ° C.), the UFP generation amount is considerably increased, and in the high temperature range than Tb, the UFP generation amount is gradually decreased.

On the other hand, the collection efficiency of UFP by the filter 64 depends on the relationship between the UFP adsorption performance (fiber material, density, etc.) by the fibers constituting the filter 64 and the speed of the air flow (wind speed) passing through the filter 64. Determined.
In the present embodiment, a range of wind speed (air volume) suitable for the performance of the filter 64 to be mounted is obtained from experiments so that UFP can be collected with higher efficiency in a low temperature region where the amount of UFP generated is large. The large fan 61 is specified as a fan that can output the air volume in the obtained range. For this reason, only the large fan 61 is rotationally driven in the low temperature range.

FIG. 6B is a diagram illustrating the operation timing of the large fan 61 and the small fan 62 during the warm-up of the fixing unit 30. The horizontal axis represents time, the vertical axis represents the air volume, and the solid line graph represents the large fan 61. The operation timing of the small fan 62 is indicated by a broken line graph.
As shown in FIG. 6B, the large fan 61 is started at time t1, and thereafter, the air volume of the large fan 61 is maintained at the reference value Qa. The air volume is proportional to the rotational speed of the motor 61a of the large fan 61, and maintaining the air volume at the reference value Qa is equivalent to the large fan 61 rotating stably. The same applies to the small fan 62.

When the time point t3 is reached, that is, when the temperature T of the fixing roller 31 rises to Tb, the power supply to the large fan 61 is cut off (driving stop). After the time t3, the high temperature range is entered.
When the air volume Q of the large fan 61 decreases to 0 (rotation stopped) (time t5), the small fan 62 starts to be activated (time t6). In the figure, an example is shown in which a little time is provided between the time point t5 and the time point t6, but the time points t5 and t6 may be substantially simultaneous.

When the air flow of the small fan 62 reaches the reference value Qb after the start of the small fan 62 (stable rotation), the large fan 61 is started again (time point t7). After the large fan 61 is started, when the air volume of the large fan 61 reaches the reference value Qa (time point t8), thereafter, both the large fan 61 and the small fan 62 are continuously rotated in a stable rotation state. The
In a state where the small fan 62 is rotating stably (after time t7), since the inertia at the time of activation does not act on the motor 62a of the small fan 62, the rotational speed can be slightly affected even by the influence of the air flow of the large fan 61. There is little disturbance and the rotation is kept constant.

  Since the large fan 61 starts to be activated while the small fan 62 is operating at stable rotation, the large fan 61 is affected to some extent by the air flow from the small fan 62. However, since the small fan 62 has a small air volume, the rotation at the start of the large fan 61 is less unstable, and the air flow from the large fan 61 having a large air volume has an influence on the activation of the small fan 62. As a result, the rotation of the small fan 62 at the time of start-up becomes unstable, and a situation in which a roaring sound is generated does not occur.

As a result, since the rotation after the start-up of each of the large fan 61 and the small fan 62 starts up smoothly, generation of a roaring sound due to unstable rotation is prevented.
In FIG. 6B, the magnitude of the airflow of the air flow flowing through the duct 63 after the time point t7 is indicated by a one-dot chain line, and both the large fan 61 and the small fan 62 are stably rotated after the time point t8. Thus, the total air volume is obtained by adding the air volumes of the two fans.

Between time t1 and time t3 (when the temperature T of the fixing roller 31 is in a low temperature range lower than Tb), only the large fan 61 is driven to rotate because the UFP that occurs frequently in the low temperature range is efficient as described above. This is because the large fan 61 is selected as a fan having an air volume suitable for being collected by the filter 64.
On the other hand, after the time t3 (when the temperature T of the fixing roller 31 is in a high temperature range equal to or higher than Tb), both the large fan 61 and the small fan 62 are rotationally driven because the temperature in the space around the fixing unit 30 is lower than the low temperature range. The reason is that the cooling around the fixing unit 30 cannot catch up with the large fan 61 alone because it becomes considerably high.

  In order to cool the surrounding space of the fixing unit 30 in a high temperature range, an air volume that is not sufficient for the large fan 61 is obtained in advance through experiments or the like, and a fan that can output the obtained air volume is specified as the small fan 62. Therefore, by rotating both the large fan 61 and the small fan 62, the temperature of the space around the fixing unit 30 does not become too high in the high temperature range where the temperature T of the fixing roller 31 is equal to or higher than Tb. Is efficiently cooled.

In this sense, the temperature Tb is a temperature after the generation amount of UFP starts to decrease from the maximum value, and is determined in advance as a temperature at which both the large fan 61 and the small fan 62 need to be operated to cool the inside of the apparatus. It can be said that it is a predetermined temperature.
In terms of cooling, instead of the small fan 62, it may be possible to use the same fan as the large fan 61 having a larger air volume. However, if the air volume becomes too large, the fixing unit 30 is cooled too much. If the heat of the fixing roller 31 is deprived due to the cooling, it is necessary to increase the power supplied to the heater 33 to compensate for the deprived heat. This leads to the consumption of extra power. For this reason, when the fixing roller 31 is equal to or higher than the temperature Tb, the temperature of the space around the fixing unit 30 does not become too high, and cooling of the fan may affect the fixing roller 31 heated by the heater 33. A small fan 62 is used here as a fan that can output an air volume that is not sufficient with the large fan 61 in order to flow an air flow with an air volume within that range to the duct 63.

In the low temperature range (between time points t1 and t3), only the large fan 61 is rotated in preference to the collection of UFP that occurs more in the low temperature range than the cooling of the surrounding space of the fixing unit 30. This is referred to as an efficiency priority period, and control for rotating only the large fan 61 is referred to as third control.
In the high temperature region (after time t3), both the large fan 61 and the small fan 62 are rotationally operated with priority given to the cooling of the space around the fixing unit 30 rather than the collection of UFP that generates less in the high temperature region. This is called the exhaust efficiency priority period. The control of the large fan 61 and the small fan 62 during the exhaust efficiency priority period is referred to as second control, and the fan is from the start of the second control (time t3) to the restart of the start of the large fan 61 (time t7). This is called the switching time zone. The temperature Tb that triggers switching from the third control to the second control is referred to as a fan switching temperature.

  In the present embodiment, an example in which the fan switching temperature Tb is higher than room temperature (about 25 ° C.) and considerably lower than the fixing temperature Ta (for example, 170 ° C.) (for example, 120 ° C.) is experimentally determined in advance is shown. However, it is not limited to this. For example, the amount of UFP generated is large until the temperature of the fixing roller 31 reaches the fixing temperature Ta, and during that time, both the large fan 61 and the small fan 62 need not be operated, and after the fixing temperature Ta is reached. When the UFP generation amount decreases, the fan switching temperature Tb can be set to the fixing temperature Ta or a temperature slightly lower than the fixing temperature Ta. For example, when the fan switching temperature Tb is set to the same temperature as the fixing temperature Ta, the third control is executed until the warm-up end (time t4), and the second control is switched to the warm-up end.

(5) Flow of Fan Operation Control FIG. 7 is a diagram showing a flowchart of fan operation control. This fan operation control is executed as a subroutine of a main routine (not shown) by the fan control unit 87 in parallel with the warm-up operation started when the printer 1 is powered on (power switch is turned on). At the start of fan operation control, both the large fan 61 and the small fan 62 are stopped.

The current temperature T of the fixing roller 31 is detected (step S1). This detection is performed by acquiring the temperature detected by the temperature detection sensor 34.
It is determined whether or not the detected temperature T is lower than the fan switching temperature Tb (step S2). When T <Tb is determined (“Yes” in step S2), the large fan 61 starts to be activated (step S3). This start-up is performed by starting the supply of power to the large fan 61.

A rotation speed signal is received from the large fan 61 (step S4). It is determined from the received rotational speed signal whether the large fan 61 has reached stable rotation (step S5). This determination is made based on whether or not the air volume of the large fan 61 has reached a rotational speed corresponding to Qa (FIG. 6B).
If it is determined that the large fan 61 has reached stable rotation (“Yes” in step S5), the current temperature T of the fixing roller 31 is detected (step S6). It is determined whether or not the detected temperature T is equal to or higher than the fan switching temperature Tb (step S7). Until the relationship of T ≧ Tb is satisfied, that is, when T <Tb, the large fan 61 is maintained in a stable rotation. Steps S1 to S7 correspond to the third control.

When it is determined that T ≧ Tb is satisfied (“Yes” in step S7) (FIG. 6A: time t3), the driving of the large fan 61 is stopped (step S8). This drive stop is performed by cutting off the power supply to the large fan 61.
It is determined whether or not the rotation of the large fan 61 has stopped (step S9). The determination of the rotation stop is made when the rotation speed signal received from the large fan 61 becomes a signal indicating zero.

When it is determined that the rotation of the large fan 61 has stopped (“Yes” in step S9) (FIG. 6 (b): time point t5), the small fan 62 starts to be activated (step S10) (FIG. 6 (b): Time t6). This start-up is performed by starting the supply of power to the small fan 62.
A rotation speed signal is received from the small fan 62 (step S11). Then, it is determined from the received rotation speed signal whether the small fan 62 has reached stable rotation (step S12). This determination is made based on whether or not the air volume of the small fan 62 has reached the rotational speed corresponding to Qb (FIG. 6B).

When it is determined that the small fan 62 has reached stable rotation (“Yes” in step S12), the large fan 61 starts to be activated (step S13) (FIG. 6B: time t7). This is equivalent to the control of starting the large fan 61 after reaching the predetermined rotational speed after starting the small fan 62 (prohibiting the start of starting until reaching the predetermined rotational speed).
After the large fan 61 is activated, a rotational speed signal is received from the large fan 61 (step S14), and when it is determined that the large fan 61 has reached stable rotation (“Yes” in step S15) (FIG. 6B). : Time t8), return. Steps S8 to S15 correspond to the second control, and the determination that the relationship of T ≧ Tb is satisfied in step S7 corresponds to the reception of operation instructions for both the large fan 61 and the small fan 62.

On the other hand, if it is determined in step S2 that T <Tb is not satisfied, that is, T ≧ Tb (“No” in step S2), steps S3 to S9 are skipped and not executed, and the process proceeds to step S10. Execute the process. An example of satisfying the relationship of T ≧ Tb immediately after the power is turned on will be described with reference to FIG.
FIG. 8A shows the fixing roller 31 when the power is turned off (time t12) after the end of the job (time t11) and then turned on again (time t13) after a short time (for example, several minutes). It is a figure which illustrates transition of temperature.

  Since the time from power-off to power-on again is short, there is little decrease in the temperature of the fixing roller 31 during the power-off period (between time t12 and t13). In the example of FIG. Is only lowered to a temperature Td slightly lower than the fixing temperature Ta. For this reason, when the warm-up is started when the power is turned on (time point t13), and step S2 is executed in parallel therewith, a relationship of T ≧ Tb is established.

  In such a case, as shown in FIG. 8B, the power supply to both the large fan 61 and the small fan 62 is cut off (driving stop) during the power-off period (between time points t12 and t13), and the time point t13. When the power is turned on, the small fan 62 starts to be activated. After the activation, when the small fan 62 reaches a stable rotation, the large fan 61 is activated (time t14). Since the small fan 62 with the small air volume is activated first and then the large fan 61 with the large air volume is activated, the activation of the small fan 62 is prevented from becoming unstable due to the operation of the large fan 61.

To determine that both the large fan 61 and the small fan 62 satisfy the relationship of T ≧ Tb when the power is turned on while driving is stopped has accepted the operation instructions of both the large fan 61 and the small fan 62. Equivalent to. Control in which the small fan 62 and the large fan 61 are started in order from the state where both the large fan 61 and the small fan 62 are stopped from driving is referred to as first control.
In the above description, whether or not both the large fan 61 and the small fan 62 satisfy the relationship of T ≧ Tb while the drive is stopped is configured to be triggered by power-on, but the present invention is not limited to this. For example, when the power supply to the heater 33 is reduced to 0 or less than normal, the power saving state is restored to the ready state where printing is possible, or after the jam occurs, the jam is released and the ready state is reached. It is also possible to adopt a configuration that is triggered by the return to the state.

<Embodiment 2>
In the first embodiment, the configuration example is described in which the large fan 61 is used as a fan that efficiently collects the UFP generated in a large amount when the temperature of the fixing roller 31 is in a low temperature range by the filter 64. On the other hand, in the second embodiment, a filter 64 having a different UFP recovery capability is selectively mounted on the duct 63 by a user or a service person (hereinafter referred to as “operator”). In this configuration, control is performed to switch the fan to be driven among the large fan 61 and the small fan 62 in accordance with the type of filter that is currently mounted. This is different from the first embodiment. ing. Hereinafter, in order to avoid duplication of description, the description of the same contents as those of Embodiment 1 is omitted, and the same components are denoted by the same reference numerals.

FIG. 9 is a diagram showing a configuration of fan information 95 in which the type of the filter 64 is associated with the fan to be operated in the low temperature range. This fan information 95 is stored in the fan information storage unit 94 (FIG. 5). Stored in advance.
In FIG. 9, types A, B,... Are listed as examples of types of filters 64, and types A, B,... Are those with the highest ability when UFP recovery ability is divided into several stages. It is used as a code that distinguishes the next most powerful one.

  The recovery capacity of UFP indicates how much UFP that is going to pass through the filter 64 can be collected (that is, the performance of the filter 64). This is increased by using a material that is easily adsorbed or by increasing the amount (density) of fibers per unit volume. On the other hand, the collection efficiency of UFP varies depending on the combination of fans as well as the performance of the filter 64 as described above.

  Therefore, if the filter 64 of different types (performance) can be selectively mounted as in the second embodiment, the UFP capture of the large fan 61 and the small fan 62 for each type of filter 64. A fan that is suitable for improving the collection efficiency is determined in advance, and only the determined fan is driven to improve the collection efficiency of the UFP regardless of the type of filter 64 attached. It becomes possible.

  In the example shown in the figure, when the currently installed filter 64 is a type A filter, it is more efficient to collect UFP when only the large fan 61 is driven when the temperature of the fixing roller 31 is low. It shows what can be done. When the fan corresponding to the type A filter 64 is the large fan 61, the fan operation control is the same as that in the first embodiment. This control is referred to as first fan operation control.

On the other hand, when the currently installed filter 64 is of type B, it is shown that the UFP can be collected more efficiently when only the small fan 62 is driven when the temperature of the fixing roller 31 is in the low temperature range. ing.
In the case of type B, the control (second fan operation control) shown in FIG. 10 is executed as the fan operation control. That is, in a state where both the large fan 61 and the small fan 62 are stopped, the small fan 62 starts to be activated at time t1. After the small fan 62 is activated, the small fan 62 is stably rotated (time point t21). Thereafter, when the time point t3 (when the temperature of the fixing roller 31 is raised to the fan switching temperature Tb) is reached, the large fan 61 is activated. To do. When the large fan 61 rotates stably (time point t22), the driving is continued in a state where both the large fan 61 and the small fan 62 are stably rotated.

Control in which the small fan 62 is activated in a state where the large fan 61 is stopped in the low temperature range between the time points t1 and t3 is referred to as fourth control, and the operation of the small fan 62 is performed in the high temperature region after the time point t3. Control that activates the large fan 61 while continuing is referred to as fifth control.
The type of filter 64 currently mounted is stored in the filter information storage unit 93 (FIG. 5) when the operator inputs filter information indicating the type from the operation panel 50. ing. That is, every time the operator replaces the filter 64, the operator performs an operation of inputting filter information corresponding to the attached filter 64 from the operation panel 50. The operation panel 50 receives an input from the operator as a reception unit, and only the latest received filter information is stored in the filter information storage unit 93. The filter information is not limited to the input operation from the operation panel 50, and may be acquired from an external terminal device via a network and stored in the filter information storage unit 93, for example.

FIG. 11 is a flowchart showing the contents of processing for selectively executing the first fan operation control and the second fan operation control, and is executed by the fan control unit 87 when the power is turned on.
Filter information indicating the type of the filter 64 currently mounted is acquired (step S21). This filter information is performed by reading out the filter information stored in the filter information storage unit 93.

  From the acquired filter information and the fan information stored in the fan information storage unit 94, a fan to be operated in a low temperature range is determined (step S22). For example, when the filter information is information indicating type A, the fan corresponding to type A is determined as the large fan 61 from the fan information, and the determined large fan 61 is determined as a fan to be operated in a low temperature range. In the case of information indicating type B, the fan corresponding to type B is determined as the small fan 62 from the fan information, and the determined small fan 62 is determined as a fan to be operated in a low temperature range.

When the large fan 61 is determined (“Yes” in step S23), the first fan operation control is executed (step S24), and the process ends. When the small fan 62 is determined (“No” in step S23), the second fan operation control is executed (step S25), and the process is terminated.
The first fan operation control is control for executing the same processing as steps S1 to S15 in the flowchart shown in FIG.

  As shown in FIG. 12, the second fan operation control is a control that executes only the processes of steps S10 to S15 in the flowchart shown in FIG. That is, in the state where the processing of Steps S1 to S15 (execution of the third control and the second control) shown in FIG. 7 is prohibited and both the large fan 61 and the small fan 62 are stopped driving, Steps S10 to S15 are performed. Only these processes are executed in order. Steps S10 to S12 correspond to the fourth control shown in FIG. 10, and steps S13 to S15 correspond to the fifth control shown in FIG.

  Thus, in a configuration in which different types of filters 64 can be selectively mounted by the operator, the fan operation control that is suitable for the filter 64 that is currently mounted, among the first fan operation control and the second fan operation control. Is automatically selected and executed. Therefore, UFP generated in a large amount in the low temperature region of the fixing roller 31 can be more efficiently removed by using the filter 64 that is currently mounted.

  In the above description, when the type of the filter 64 is type B, the second fan operation control that starts in the order of the small fan 62 and the large fan 61 is executed. However, the present invention is not limited to this. For example, in the case where the deterioration of the filter 64 due to clogging of the UFP becomes remarkable during the period from when the type B filter 64 is new to the end of its service life, It is also possible to switch to one fan operation control.

  Specifically, only the large fan 61 is operated in place of the original small fan 62 in the low temperature range between the time points t1 and t3, and the UFP collection efficiency is higher than that of the small fan 62. Then, in the high temperature range after time t3, after the large fan 61 stops rotating, the small fan 62 and the large fan 61 are sequentially activated. In this way, even if the filter 64 is further deteriorated, it becomes possible to maintain the UFP collection efficiency in the low temperature region as much as before the deterioration, and in the high temperature region, the large fan 61 and the small fan 62 can be maintained. By both operations, the space around the fixing unit 30 can be cooled before and after the filter 64 is deteriorated.

The deterioration of the filter 64 progresses as the amount of collected UFP accumulated in the fiber increases. On the other hand, UFP frequently occurs during the warm-up of the printer 1. As the cumulative number of warm-ups of the printer 1 increases, the amount of UFP accumulated in the filter 64 increases.
Therefore, the time point at which the deterioration of the filter 64 becomes noticeable is defined by the cumulative number of warm-ups, and the number of warm-ups in the printer 1 is accumulated after the filter 64 is new, and the cumulative number reaches a predetermined number. The second fan operation control is executed during the period up to and after the predetermined number of times is reached, the control can be switched to the execution of the first fan operation control. This predetermined number of times is determined in advance by experiments or the like so that the UFP collection efficiency can be secured at a certain level in the low temperature range before and after the deterioration of the filter 64.

<Modification>
As described above, the present invention has been described based on the embodiment. However, the present invention is not limited to the above-described embodiment, and the following modifications may be considered.
(1) In the above-described embodiment, in the second control (FIG. 6B), the small fan 62 is started to start (time t6) after the rotation of the large fan 61 is stopped. However, the present invention is not limited to this. .

  As the second control, for example, instead of stopping the rotation of the large fan 61, the air flow of the large fan 61 is decreased from the reference value Qa to the predetermined value Qc as shown in FIG. ). Decreasing the air volume of the large fan 61 from Qa to Qc is equivalent to decreasing the rotational speed of the large fan 61 (substantially, the motor 61a) from the rated rotational speed Va to a predetermined speed Vc.

  When this configuration is adopted, the small fan 62 is activated even if the air pressure on the side of the intake port 62p of the small fan 62 that is not driven is lower than that on the side of the air outlet 62z. A predetermined speed Vc (air volume Qc) is determined in advance by experiments or the like within the range of the rotational speed of the large fan 61 so as not to affect. For example, when the rotation speed range of the large fan 61 is 0 to (Va / 3) and does not affect the start of the small fan 62, the relationship 0 <Vc ≦ (Va / 3) is satisfied. A predetermined speed Vc can be determined.

  After the small fan 62 is started, when the small fan 62 reaches a stable rotation, the rotation speed (or air volume) of the large fan 61 is changed from the speed Vc (or air volume Qc) to the original speed Va (or air volume at the stable rotation) at time t7. The large fan 61 is controlled to return to Qa). In this control, after the small fan 62 is activated, after the predetermined rotational speed Vb is reached, the large fan 61 is returned to the original rotational speed Va (returning to the speed Va is prohibited until the speed Vb is reached). Control.

Decreasing the rotation speed (or air volume) of the large fan 61 to Vc (or Qc) is that the supply voltage to the large fan 61 is lower than the value E1 at normal time (when rotating at the rated rotation speed Va) by a certain amount. This is done by switching to voltage E2. A circuit configuration capable of changing the rotation speed of the motor 61a can be used.
When the second control of the modification (1) is used, it is not necessary to wait for the small fan 62 to start until the rotation of the large fan 61 is completely stopped. Specifically, the activation of the small fan 62 can be started at time t9 immediately before time t5 in FIG. For this reason, the start of the small fan 62 can be started earlier by the time between the time points t9 and t5 than the configuration in which the start of the rotation of the large fan 61 is triggered.

Since the start of the small fan 62 can be started earlier, the time point t7 for returning the rotation speed of the large fan 61 to the original time is also brought forward, and the exhaust heat in the apparatus due to the operation of both the large fan 61 and the small fan 62 is accelerated. It is possible to start and cool down the apparatus more efficiently.
(2) In the above-described embodiment, the configuration example for controlling the two fans 61 and 62 having different air volumes has been described. However, the present invention is not limited to this. For example, even in a configuration in which three fans having different air volumes are provided, the above-described fan operation control can be applied as control for two fans having a large air volume and those having a small air volume.

Specifically, in the configuration in which the fans A, B, and C have a relationship in which the air volume increases in this order, when all the fans are stopped, the fans A, B, and C are activated in this order. The first control is applied in the order of fans A and B.
Further, when only the fan C is operating first, after the rotation of the fan C is temporarily stopped, the fans A and B are started in this order, and then the fan C is started. Starting the fan A after stopping the rotation of the fan C and then starting the fan C is the application of the second control.

(3) In the above embodiment, the blower is used as a fan. However, the present invention is not limited to this. For example, a fan such as a propeller fan or a cross flow fan can be applied.
In addition, the air passage 69 of the duct 63 is bent in the middle of passing through the first duct portion 71, the second duct portion 72, and the third duct portion 73 (FIG. 2). For example, a straight pipe may be provided between the intake port 63a and the discharge port 63b.

  Further, when the amount of UFP generated is small and it is not necessary to collect by the filter 64, the filter 64 may be omitted. Even in this configuration, the third control is executed from the start of warm-up until the temperature of the fixing roller 31 rises to a predetermined temperature Tf (for example, about 100 ° C.), and the control is switched to the second control when the temperature becomes equal to or higher than the temperature Tf. be able to. Regardless of UFP, when the apparatus belongs to a low temperature range lower than the predetermined temperature Tf, only the large fan 61 is operated to suppress cooling in the apparatus, while if the apparatus belongs to a high temperature range equal to or higher than Tf, the large fan 61 is operated. Both the small fan 62 and the small fan 62 can be operated to promote cooling in the apparatus.

  (4) In the above-described embodiment, the configuration example in which the small fan 62 is disposed so as to be slightly closer to the outlet 63b of the duct 63 than the large fan 61 has been described. However, the present invention is not limited to this. . For example, the large fan 61 can be configured closer to the discharge port 63b of the duct 63 than the small fan 62, and the distance between the large fan 61 and the small fan 62 is equal to the discharge port 63b of the duct 63. It can also take the structure arranged side by side so that it may become.

In any case, the large fan 61 and the small fan 62 in the air passage 69 of the duct 63 are in a positional relationship such that the air pressure at the intake port 62p side of the small fan 62 is lower than that at the air outlet 62z side. The present invention can be applied to a configuration in which the fan 62 is arranged.
(5) In the above embodiment, in the second control (FIG. 6B), the fact that the small fan 62 after starting has reached stable rotation (having reached a predetermined rotational speed Vb (FIG. 13)). The start of the large fan 61 is started (time t7) as an opportunity, but is not limited to this. If the configuration does not affect the rotation of the small fan 62 that has been started, the large fan 61 starts from the time before the small fan 62 starts stable rotation (for example, the time t10 in FIG. 6). May be started.

  (6) In the above-described embodiment, the configuration example including the fan exhaust unit 60 for cooling the peripheral space of the fixing unit 30 and removing the UPF has been described. However, the present invention is not limited to this. For example, the present invention can be applied to a configuration in which ozone generated in the peripheral space is discharged out of the apparatus when the photosensitive drum 12 is charged by discharging of the charging unit 16 of the image forming unit 10. Specifically, during the execution of a job with a small number of prints, for example, a few, only the large fan 61 is rotationally driven, and the job for continuously printing a large number of recording sheets S exceeding 100 is executed. Among them, since the amount of ozone generated as the job execution time increases, the ozone can be efficiently discharged by switching to the rotational drive of both the large fan 61 and the small fan 62. As the filter 64, an ozone filter that removes ozone is used.

  (7) In the above embodiment, the example in which the image forming apparatus according to the present invention is applied to a tandem type color printer has been described. However, the present invention is not limited to this. The present invention can be applied to electrophotographic image forming apparatuses such as copying machines, facsimile apparatuses, and MFPs (Multiple Function Peripherals), and is not limited to the electrophotographic system. The present invention can be applied to an exhaust device that discharges the air and an image forming apparatus including the exhaust device.

  Further, the contents of the above embodiment and the above modifications may be combined as much as possible.

  The present invention can be used for an exhaust device that exhausts air inside an image forming apparatus to the outside of the apparatus.

DESCRIPTION OF SYMBOLS 1 Printer 30 Fixing part 31 Fixing roller 33 Heater 34 Temperature detection sensor 36 Upper space of fixing part 60 Fan exhaust part 61 Large fan 61p, 62p, 63a Inlet 61z, 62z Air outlet 62 Small fan 63 Duct 63b Outlet 64 Filter 69 Air passage 86 Heater control section 87 Fan control section 91 Rotation / stop instruction section 92 Stable rotation determination section 93 Filter information storage section 94 Fan information storage section 95 Fan information

Claims (9)

An exhaust device that takes in air in an image forming apparatus into a duct and discharges the taken-in air out of the image forming apparatus from the duct,
A first fan and a second fan having a smaller air volume,
Control means for controlling the first and second fans;
With
When the first fan operates in the air passage in the duct while the second fan is not driven, the first fan and the second fan are blown toward the inlet side of the second fan. Arranged in a positional relationship where the air pressure is lower than the outlet side,
The control means includes
When the operation instructions for both the first and second fans are received, if both fans are stopped, the first control for starting the first fan is executed after the second fan is started. ,
When the first fan is operating and the second fan is stopped driving, the rotation of the first fan is stopped or the atmospheric pressure decreases due to the operation of the first fan. The rotation speed is reduced to a predetermined speed so as not to affect the activation of the second fan, the second fan is activated, and then the first fan is activated or based on the rotation speed. An exhaust system that performs a second control to be returned. The control means includes
The temperature in the apparatus is acquired from the image forming apparatus, and when the acquired temperature in the apparatus is lower than a predetermined temperature, the third control is performed to operate the first fan and stop driving the second fan. And
2. The exhaust system according to claim 1, wherein when the acquired temperature rises and reaches the predetermined temperature, this is accepted as the operation instruction, and the execution is switched from the third control to the execution of the second control. The control means includes
When it is determined that the acquired temperature is equal to or higher than the predetermined temperature while both the first and second fans are stopped, the operation is accepted as the operation instruction and the first control is executed. The exhaust device according to claim 2, wherein The image forming apparatus includes a fixing unit that thermally fixes an unfixed image formed on a recording sheet by a fixing member heated by a heater,
The fixing unit may be accompanied by generation of ultrafine particles during driving,
An air inlet of the duct is located in the vicinity of the fixing unit, and air around the fixing unit is taken into the duct as air in the image forming apparatus,
The exhaust device according to claim 2, wherein the exhaust device includes a recovery unit that recovers ultra fine particles contained in the air taken into the duct. The image forming apparatus further includes a detection unit that detects a temperature of the fixing member, and a heater that controls the heater based on the detection temperature of the detection unit to raise the temperature of the fixing member to a fixing temperature necessary for heat fixing. A control unit,
The temperature of the fixing member and the generation amount of ultrafine particles have a relationship in which the generation amount of ultrafine particles rises to a maximum value as the temperature of the fixing member moves from low temperature to high temperature, and then decreases.
The control means acquires the detected temperature of the detection unit as the temperature in the device,
The predetermined temperature is a temperature after the generation amount of ultrafine particles starts to decrease from the maximum value, and is a temperature at which it is necessary to cool both the first and second fans to cool the image forming apparatus. The exhaust device according to claim 4, wherein the exhaust device is determined. The collection unit is a filter that allows the air in the duct to pass through, and a different type of ultrafine particle collection capability is mounted on the duct so that it can be replaced by an operator.
The control means includes
According to the type of filter that is currently installed, the fan to be operated when the detected temperature is lower than the predetermined temperature is determined among the first and second fans,
When the first fan is determined, the third control is executed when the detected temperature is lower than the predetermined temperature, and when the predetermined temperature is reached, the second control is switched to,
When the second fan is determined, execution of the third control and the second control is prohibited, and the first fan is stopped when the detected temperature is lower than the predetermined temperature. The fourth control for starting the second fan is executed, and when the predetermined temperature is reached, the control is switched to the fifth control for starting the first fan while continuing the operation of the second fan. The exhaust device according to claim 5. The control means includes
For each different type of filter, a storage unit is provided that stores fan information in which a fan to be operated when the detected temperature is lower than the predetermined temperature among the first and second fans is associated. ,
The filter information indicating the type of the filter that is currently installed is acquired, the fan corresponding to the filter type indicated by the acquired filter information is determined from the fan information, and the detected temperature of the determined fan is the predetermined temperature. The exhaust device according to claim 6, wherein the exhaust device is determined to be a fan that is operated when the temperature is lower. The control means includes
The start of the first fan is started after the second fan reaches a predetermined rotational speed after the start, or the rotational speed is returned to the original speed. The exhaust device according to item.   An image forming apparatus on which the exhaust device according to claim 1 is mounted.

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